Apple introduced the butterfly keyboards in the 2015 MacBooks and 2016 MacBook Pros. The thinner mechanisms beneath each key were designed to apply more pressure, thereby increasing responsiveness and lowering the profile. But it also led to sticky keys, repeating characters, keystrokes not appearing, and complete keyboard failures.
https://www.techspot.com/news/97014-apple-giving-macbook-owners-faulty-butterfly-keyboards-up.html?utm_source=dlvr.it&utm_medium=blogger
https://www.techspot.com/news/97014-apple-giving-macbook-owners-faulty-butterfly-keyboards-up.html?utm_source=dlvr.it&utm_medium=blogger